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I often get asked by people as to what the role is of the pianos outer cabinet/ its supporting structure and the plate, in regards to the tone. I have heard numerous theories about this that range from the point that it serves the same purpose as a sound system speakers structure...nil. I have also heard that the predominant use of spruce in the structure of a Bosendorfer adds warmth to the over all tone.

Do you think the structure plays a beneficial role beside the soundboard, or can a pianos' structure feasibly be made out of concrete and rebar and still reasonably retain its tone with a properly installed wood soundboard/bridge?

If you got humorous replies, it could be that most people think that all pianos are actually made of real wood. In fact, essentially all pianos from entry level to mid grade (verticals) use MDF, laminates, chip board (affectionately called Beaver Barf by a friend of mine), and a host of other materials for their cases. Yamaha and Kawai uprights use plastic for the trim moldings, even in the high level uprights. I have seen sheet metal case parts (legs) on an older Kawai, if memory serves.

Regarding Emery's question - it sure would be interesting to hear pianos with cabinetry made of ferro-cement or the like.

I am doubtful about the positive tonal impact of the spruce used in grand rims. Having visited the factory, I saw how the thin spruce core was sandwiched on both sides with 3 mm K-3 fibre board. Then on top of that, a strong veneer of melamine provides a stable foundation for the thick layers of polyester. I am not convinced that the spruce in the middle can sing any more than the beef patty in a teen burger....

• they are built using the highest possible proportion of sound-spruce"

I do perceive a unique type of sound coming from a Bosie so I don't believe this is an highly exagerated or false claim from the company. Its just that I have seen extremely high end speakers ($20K+)and they use high density particle board in their box construction, just like the cheap ones do. An engineer explained that the efficiency of the woofer is helped by a containing structure closely emulating an infinate mass (heavy density).

MDF is a great absorber of vibration and tends not to generate harmonics. It is great for speaker enclosures due to those characteristics, since the material doesn't color the sound being reproduced by the drivers mounted in the enclosure. (I used to design and build those systems in another life.)

Personally, I like the old piano case work in many of the uprights which had light-weight panels. Usually the thicker portions which framed the lighter insets were 5-ply lumber core and had poplar as the lumber core. It is a light wood. Panels like that could vibrate. What real benefit that would have is a complex issue, but at least some of that internal sound could have a fighting chance of getting out to someone's ears.

Today manufacturers experiment with the last elements that can radiate , the keybed, the rim and braces. (pinblock of course)

I suspect that something have to filter the too abrubpt tone that comes from the soundboard only. To shape it while helping it to be less incisive.

Then 2 views still remain :

The rim and structure may be firm and send back maximum energy, in that case the plate is active and resonate in the tone (and is suspended on dowels , have thin braces...)

The case is more active, then the plate is more massive and damped.

(unless there is no real relation between the plate design and behaviour and the radiating role left to the case...)

Old plates had a different iron (phosphorous, local material) than today, and I have read that 2 different iron are used today.I have the reference names , not sure they mean something in English

Back to case and accessoiries (on verticals, the pedal mechanisms, the aluminium action rails are resonant, not that they radiate much, but they vibrate and add some spring tone

Some good verticals have almost no case, thin mdf planks, they tend to have a clearer tone ans seem to ne their plate is stronger. Others have yet thick panels an can have a warmer tone because of that. Possibly more a mass question then, more mass, lower frequencies can have a little benefit.

The day I read / speak German enough I sure will know more about those cultural trades. It should be interesting, as I seem to notice that reverse engineering + logical thinking are leaving much aspects unsuspected, on pianos. As I have noticed with some lack of elegance on pianos tending to preserve energy, to optimise the design, to raise poiwer/dynamics. Overly bright, too precise, less "singing"

As the abscence of cutoff bars can give sone free bonus for the warm side of tone, not because it is better or a better design, but because the sound is more accepting pianist mistakes and room acoustics ...

Edited by Kamin (01/23/1305:36 AM)

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Interestingly enough, I presume that some time in the near future someone may precisely map out the structure (along with the soundboard) in regards to frequency response/resonance. There is a high tech instrument available for this now called a laser dopper vibrometer. It is used for measuring and mapping (with software) the surfaces of objects extremely precisely for vibration. It is extremely accurate and has been used in the auto industry now for a few years to analyze resonance of motor parts and body panels. Here is a photo of what it does....

There is certainly a great deal of opinion about the role of the structure in the tone of the piano. I spent some time working at a Boosie dealer, helping to prepare for a sale, and listened to the salesman when taking a break from the tuning in the next room.

He walked to a Boosie and softly knocked on the rim. The piano produced an audible 'Bong! Bong!'. Then he walked to a used Steinway on the floor and knocked again; 'Thud. Thud.' and proceeded to explain that the Boosie approach to building regarded the rim as a part of the tonal structure, the complexity of sound from all the parts and structure creating the unique signature sound.

Heck of a salesman, eh?

There was also a Schimmel Transparent on the floor...which has a 3"-plastic rim. When showing THAT piano, the salesman tapped the case, producing a dull 'Thunk', and explained that all the energy of the soundboard and strings was reflected back into the soundboard by the solid rim. Producing that amazing signature sound. And it sure looked pretty when the lights on the rim were turned on....